The DropDMG commands in the Services menu will become available the next
time you log in.

DropDMG includes an optional dropdmgcommand-line tool. It can be
installed as follows:

If you downloaded DropDMG direct from C-Command

Go to the Advanced tab of the Preferences window and click the
Install “dropdmg” Tool button. DropDMG will ask for an administrator
password, as it needs to copy the dropdmg file to the protected
/usr/local/bin or /usr/bin folder.

If you purchased DropDMG from Apple’s Mac App Store

Open the Terminal application. To install the command-line tool, enter these
commands: